PurposeUrocanic acid (UCA) is a major ultraviolet (UV)-absorbing endogenous chromophore in the epidermis and is also an efficacious immunosuppressant. The anti-inflammatory and cytoprotective effects of cis-UCA were studied in ocular surface cell cultures exposed to UV-B irradiation. MethodsHuman corneal epithelial cells (HCE-2) and human conjunctival epithelial cells (HCECs) were incubated with 10, 100, 1,000, and 5,000 μg/ml cis-UCA with and without a single UV-B irradiation dose. The concentrations of IL-1β, IL-6, IL-8, and TNF-α in the culture medium and caspase-3 activity in the cell extract sampled were measured by enzyme-linked immunosorbent assay (ELISA). Cell viability was measured by the colorimetric MTT (3-(4,5-dimethyldiazol- 2-yl)-2,5-diphenyltetrazolium bromide) assay. ResultsUV-B irradiation multiplied interleukin IL-6 and IL-8 secretion levels in HCE-2 cells and HCECs as analyzed with ELISA. Cell viability as measured by the MTT assay declined by 30%–50% in HCE-2 cells and by 20%–40% in HCECs after UV-B irradiation. Moreover, UV-B increased caspase-3 activity in both cell types as analyzed with ELISA. Treatment with 100 μg/ml cis-UCA completely suppressed IL-6 and IL-8 secretion, decreased caspase-3 activity, and improved cell viability against UV-B irradiation. No significant effects on IL-6 or IL-8 secretion, caspase-3 activity, or viability of the non-irradiated cells were observed with 100 μg/ml cis-UCA in both cell types. The 5,000 μg/ml concentration was toxic. ConclusionsThese findings indicate that cis-UCA may represent a promising anti-inflammatory and cytoprotective treatment option to suppress UV-B-induced inflammation and cellular damage in human corneal and conjunctival epithelial cells.

Purpose In vitro studies have shown anti‐inflammatory and cytoprotective effects of cis‐urocanic acid (cis‐UCA) in human ocular epithelial cells exposed to UV‐B irradiation. In this study, we aimed to investigate the efficacy of topical cis‐UCA against compound 48/80 induced eye irritation in a rat model. Methods Adult Wistar rats in groups of six animals were treated with 1000 µg/ml compound 48/80 in both eyes. Cis‐UCA 0.5% solution, corticosteroid dexamethasone 1 mg/ml (Oftan® Dexa), antihistamine ketotifen 0.25 mg/ml (Zaditen), or PBS was applied in both eyes at time points 0.5, 6, and 12 h after application of compound 48/80. Clinical signs of ocular inflammation were evaluated by scoring from photographs by ophthalmologist 1, 6, 12, and 24 h after the last drug application. Results Cis‐UCA solution attenuated conjunctival hyperemia in compound 48/80 irritated eyes equally well compared to dexamethasone and ketotifen. At time points 12 and 24 h, the mean decrease in severity score was 50% and 40%, respectively, for the cis‐UCA group. Redness of the eyelid margin was prevented best by ketotifen at 1‐h time point, whereas cis‐UCA and dexamethasone almost completely abolished lid redness at 6, 12, and 24 h. Conclusion These results suggest that cis‐UCA has an anti‐inflammatory effect in acute eye irritation, which is comparable to corticosteroid dexamethasone and antihistamine ketotifen.

Purpose Cis‐urocanic acid (cis‐UCA) is an endogenous small molecule of the skin. Preclinical data suggest that topical cis‐UCA could be used as an anti‐inflammatory treatment in ophthalmology. We investigated the safety, tolerability and pharmacokinetics (PK) of cis‐UCA in healthy adults in a randomised, double‐blind and placebo‐controlled phase 1 study. Methods The 37 subjects in 3 groups received either 0.5% or 2.5% cis‐UCA eye drops, or placebo. In part I, the eye drops were administered on one eye 3x in one day. In part II, the same subjects received the same eye drops on both eyes 3x a day for 14 days. Clinical evaluations included complete physical examination and safety laboratory tests, physical examination of the eyes, and ocular comfort rating by 5 parameters. Results Both cis‐UCA eye drops were safe and well tolerated throughout the study. None of the ocular safety parameters differed between cis‐UCA and placebo. Of the ocular comfort rating, only burning of the eyes was significantly higher with cis‐UCA than with placebo; however, this reaction was mild, transient and infrequent in all cases. PK analysis showed that 2.5% cis‐UCA eye drops may be absorbed after repeated ocular dosing, as 7/12 subjects in this group had low cis‐UCA levels (< 10 µg/ml) in the urine. However, plasma cis‐UCA levels were negligible. Conclusion The observed good local and systemic safety and tolerability of cis‐UCA eye drops warrants further clinical studies in patients with inflammatory ocular diseases. Commercial interest

Purpose:The cornea is sensitive to ultraviolet B (UV-B) radiation-induced oxidative stress and inflammation. Its clinical manifestations are photokeratitis and climatic droplet keratopathy. Urocanic acid (UCA) is a major endogenous UVabsorbing chromophore in the epidermis and it is also an efficacious immunosuppressant. We have previously shown that cis-UCA can suppress UV-B-induced interleukin-6 and −8 secretion and cytotoxicity in human corneal epithelium (HCE) cells. In the current study, we further wanted to investigate the effects of cis-UCA on UV-B-induced inflammatory and apoptotic responses in HCE-2 cells, focusing on the nuclear factor kappa B (NF-κB) and AP-1 (subunits c-Fos and c-Jun) signaling pathways. Methods: After exposing HCE-2 cells to UV-B and cis-UCA, DNA binding of c-Fos, c-Jun and NF-κB was measured with ELISA. In addition, the endogenous levels of phosphorylated stress-activated protein kinase/c-Jun N-terminal kinase (phospho-SAPK/JNK) and phospho-c-Jun were determined. The proliferative capacity of HCE-2 cells was also quantified, and the cytotoxicity of the cis-UCA and UV-B treatments was monitored by measuring the release of lactate dehydrogenase enzyme in the culture medium. Results: UV-B irradiation induced the binding of transcription factors c-Jun, c-Fos, and NF-κB to DNA. Cis-UCA inhibited the binding of c-Jun and c-Fos but not that of NF-κB. Moreover, UV-B increased the levels of phospho-c-Jun and phospho-JNK, and the expression of both was attenuated by cis-UCA. Cis-UCA also alleviated the UV-B-induced apoptosis and proliferative decline in human corneal cells. Conclusions:The results from this study suggest that cis-UCA suppresses JNK signaling pathway, which provides potential for treating UV-B-induced inflammatory defects in human corneal cells.